Metal cans such as aluminum cans are commonly used as containers for a wide variety of products. After the cans are formed, they are typically washed with various cleaners to remove aluminum fines and other contaminants from the surface. One undesirable result of these treatments is that water often is retained on the clean, rinsed metal cans which represents a major heat load for a dry off oven. For example, about 2.5 grams of retained water per metal can at a production rate of 2500 cans/minute represents over 200,000 kcal/hr. (8000 BTU/hr.) of energy input. Reducing the water load reduces the energy required. Additionally, faster drying may also allow an increase in production rate.
Conventional washes frequently result in a surface finish on the outside of the cans which has a deleterious effect on the efficient movement on the cans through the conveyor systems and onto or off the printer mandrels. It is important, therefore, in the can processing industry, and in particular, the aluminum can processing industry to reduce the coefficient of friction on the outside surface of the cans to improve their mobility without adversely affecting the adhesion of printing, paints or lacquers applied thereto. Cans characterized as having poor mobility generally have higher coefficients of static and kinetic friction. In the commercial can processing operation, there are numerous locations where the cans stop moving momentarily and must start again from rest. The mobility problem is particularly important when the cans are loaded on and ejected from the mandrels of high-speed printers. Other locations in the manufacturing process where the mobility problem is evident is where cans flow through the single file conveyors called "single filers". A high coefficient of static friction generally prohibits an increase in line speed, production speed and production output, results in frequent jammings and printer misfeed problems, and a general loss of production due to increased rates of damage to the cans.
A reduction in the coefficient of static friction improves can mobility through the conveyor systems, especially the single filers. A reduction in the coefficient of static friction also results in reduced printer rejects. It is therefore desirable to reduce the liquid residue remaining on cans after various aqueous treatments and to improve the mobility of the cans through the can processing equipment.
It is known to utilize various surfactants such as nonionic surfactant polyols for machine dishwashing operations. For example, a group of commercially available nonionic polyol surfactants available under the trade designation Pluronic including Pluronic L62, L43, L62D, L63, L63D, L72, L92 and L103 are reported to be rinse aids capable of providing uniformly good wetting and rapid drainage on glass surfaces thereby preventing drying lines. (BASF/Wyandotte Technical Bulletin "The Wonderful World of Pluronic Polyols", U.S. Library of Congress, No. 70-150738, 1971.) A group of rinse aid formulations suggested as being useful in commercial as well as home dishwashers are described in another Technical Bulletin from BASF Corporation, entitled "Performance Chemicals for Rinse Aid Formulations" (4 pages). This Bulletin suggests that most rinse aids contain a nonionic surfactant and one or more hydrotropes or coupling agents. Pluronic L10 surfactant is reported to be useful as a rinse aid alone with no hydrotrope. Hydrotropes are added to rinse aid liquids because nonionic surfactants are often partially insoluble in water at the desired concentrations. The hydrotropes increase the solubility of the surfactant in water. Examples of hydrotropes described in this bulletin include alkylnaphthylene sulfonates, dialkyl sulfosuccinate esters and oxyethylated straight chain alcohols. However, some nonionic hydrotropes such as propylene glycol and isopropyl alcohol, and urea are reported as generally ineffective solubilizers. The Bulletin includes a Formulations Selection Grid intended to provide a basic guide of various combinations of Pluronic materials which can be utilized in rinse aid formulations.
In another undated technical bulletin published by BASF (4 pages) entitled "Rinse Aid Formulary", rinse aid formulations are proposed for high temperature machines, low temperature machines and hard water. Formulations are also suggested which contain low actives (10 wt. percent surfactant).
U.S. Pat. No. 3,082,172 describes a defoaming rinse composition useful in machine dishwashing which contains a synthetic organic polyethenoxy nonionic surface active agent (such as Pluronic L63) and a particular polyoxyalkylene glycol mixture described as consisting of a product which statistically represented has a plurality of alternating hydrophobic and hydrophilic polyoxyalkylene chains, the hydrophilic chains consisting of oxyethylene radicals linked one to the other and the hydrophobic chains consisting of oxypropylene radicals linked one to the other. This statistical mixture is prepared generally by condensing propylene oxide with propylene glycol to form a polyoxypropylene glycol, and thereafter condensing ethylene oxide with the polyoxypropylene glycol following by condensing with propylene oxide.
U.S. Pat. No. 4,560,493 describes a liquid residue reducing composition which comprises an aqueous solution containing an effective amount of octane-1-phosphonic acid or a water-soluble salt thereof.